ESFAS Flashcards
(42 cards)
Discuss the basis for ESFAS.
Limits core damage and minimize offsite releases during design bases events by the actuation of systems designed to provide core cooling, establish containment isolation, and protect containment integrity
List the inputs to ESFAS.
- RWT level (4)
- Pzr pressure (4)
- Ctmt pressure (4)
- Ctmt radiation (4)
- SG A pressure (4)
- SG B pressure (4)
Discuss what is contained by the four ESFAS Measurement Channels (MA, MB, MC, MD).
- Trip bistables.
- Isolation modules.
- Auto and manual test circuits
Discuss what the two Actuation Trains (SA & SB) each contain.
- Actuation modules with logic matrix.
- Isolation modules.
- Auto and manual test circuits.
- Output relays.
- A separate enclosure for “C” component actuation circuitry.
- Each train has parallel output relays for “C” CCW, ICW, and Charging pump.
Discuss EDFAS interfaces.
RPS Instrumentation inputs that is shared.
a) Pressurizer pressure
b) Containment pressure
c) S/G pressure A
d) S/G pressure B.
* Radiation Monitoring System shares CIS monitors.
* ATWS/DSS shares PZR Pressure
Discuss the ESFAS Measurement Cabinets.
- Four measurement cabinets (MA, MB, MC, MD) are located behind RTGB 106 [206] separated by metal barriers.
Channel MA: ‘A’ Train Power: (MA instrument bus)
Channel MC: ‘A’ Train Power: (MC instrument bus)
Channel MB: ‘B’ Train Power: (MB instrument bus)
Channel MD: ‘B’ Train Power: (MD instrument bus) - ATI located in {MA Cabinet on Unit 1} and [SA Actuation Train on Unit 2]
If an ‘A’ MSIS signal is generated, what indications will be present?
- The ‘A’ MSIS handswitch “RED” light will illuminate. The ‘B’ MSIS handswitch “RED” light will NOT illuminate, but the ‘B’ train MSIS components will reposition.
- No matter which train gets the actuation signal, interposing relays ensure actuation of both trains of components
How are ESFAS bistables tripped?
UNLIKE RPS, WE DO NOT PULL THE TRIP BISTABLES FOR ESFAS
WE ONLY PULL THE ISOLATION MODULES*
Discuss Auto Test Insertion Module (ATI).
- {Located on Panel MA} [Located on Panel SA]
- Continuously monitors the ESFAS operability by performing on-line testing of the ESFAS circuitry.
- Accomplishes by continuous “pulsing” of actuation circuitry:
- Under-pulse: A 5% under setpoint signal to check for no actuation.
- Over-pulse: A 5% over setpoint pulse to check for actuation
- The ATI inserts signals into 2/4 bistable actuation flowpaths:
a) It inserts an under pulse; and then monitors that the bistable DOES NOT trip
b) It inserts an an over pulse; and then monitors that the bistable DOES trip - Why doesn’t the ATI module signal generate an ESFAS actuation signal?
The ATI test signals only trip the bistables/actuation modules for 2 milli-seconds
a) Output relays need signal present for ~ 30 milli-seconds to actuate
b) Signal resets before output relays can “actuate” on the signal
c) No actual component actuations occur
Discuss ATI Test LEDs.
- Not illuminated – Means bistable tripped on under-pulse.
- “Constantly” illuminated or Illuminated for a longer time – means failure to trip on over-pulse.
- Either results in Annunciator alarm and indicator lights on ATI panel.
- Test Panel is for I&C to periodically test and verify the B/S trip setpoints
Discuss ESFAS Actuation Cabinets.
- Two trains (SA, SB) with 2 cabinets per train
- Each cabinet uses auctioneered power supplies to ensure the loss of one power supply will not cause an actuation
- Cabinet SA: Dual Powered from MA & MC instrument buses
- Cabinet SB: Dual Powered from MB & MD instrument buses
- Actuation modules:
a) Input to the actuation module is isolation module output
b) Develops the 2/4 actuation logic
c) Logic signal development from B/S to Actuation Logic is “electronically” generated and passed (i.e., no relays)
Discuss ESFAS Signal Flowpath.
Instrument Channels
2/4 Logic Matrix
Actuation Module
Output Relays
Equipment Operation
Discuss ESFAS Block Modules.
- Output is signal to actuation relays.
- Applicable to SIAS and MSIS only.
- Requires 3/4 logic to block – meaning you must have 3/4 channels at the block setpoints
Discuss ESFAS Blocking.
- Requires key switch manipulation to block the applicable ESFAS signal
- Amber light lit above Block key switch
- Annunciator should light for Block permissive
- When switch is taken to block, then red block light should come on and amber light will go out
- Block annunciator will also come in.
Discuss ESFAS Manual Actuation/Reset Pushbuttons.
- It is a two function switch which will allow actuation or resetting of SIAS or CIAS
- Signal actuation requires two actions. First a pushbutton must be held depressed and then a control switch is taken to “Actuate”
- For reset, positioning of the switch to the “Reset” position is all that is required. (Assuming no signal is present, or signal has been blocked)
- To reset an ESFAS signal: You must either block the actuation signal, or not have the signal present.
- Can’t block containment pressure into SIAS [MSIS]
Discuss EOP-99 additional reset criteria.
SIAS
Unit 1
CTMT Pressure < 4 psig and not rising
Low RCS pressure input met or blocked
Unit 2
CTMT pressure < 3.4 psig and not rising
Low RCS pressure input met or blocked
CIAS
Unit 1
CTMT Pressure < 4 psig and not rising
CTMT Radiation is < 8 REM and not rising
SIAS not actuated or is reset
Unit 2
CTMT pressure < 3.4 psig and not rising
CTMT Radiation is < 8 REM and not rising
SIAS not actuated or is reset
MSIS
Unit 1
Low SG Pressure input met or blocked
Unit 2
Low SG Pressure input met or blocked
CTMT pressure < 3.4 psig and not rising
CSAS
Unit 1
No extra criteria
Unit 2
No extra criteria
Discuss ESFAS Normal / Isolate Switches.
- Allows remote operation of components and isolation from Control Room circuitry
- Incorporated into component circuitry so that a fire in the control room would not result in unwanted component actuations during a control room evacuation
- Switch is normally in “Normal”
a) Electrically inserts the ESFAS auto initiation circuitry into component control circuits.
b) Administrative controls ensure these switches properly positioned. - Normal/Isolate in “Isolate”;
a) This position defeats all auto ESFAS signals by electrically “removing” the auto initiation circuitry from component control circuits.
b) Also electrically removes all control room circuitry from the component control circuitry.
c) Component would be rendered inoperable
d) “Isolate” position annunciated when in “Isolate.”
Discuss Safety Injection Actuation Signal.
Designed to assist with reactivity control and inventory control post RX Trip with a LOCA by injecting borated water into the RCS.
Auto initiated from:
PZR Press Low (2/4) {≤ 1600}[≤ 1736] psia
CNMT Press Hi (2/4) {≥ 5.0} [≥ 3.5] psig
De-energizes the bistable to actuate
Can be manually actuated from the RTGB
Block Feature:
* Via a key switch. Train specific capability. Allows a controlled C/D without SIAS actuation
* Can only occur when 3/4 PZR pressure channels decrease to {≤ 1725} [≤ 1836] psia
* Blocks pressurizer pressure input only.
* Failure to Block SIAS (or MSIS) during a cooldown would result in a full actuation and an LER to the NRC
* Can still manually actuate if blocked – blocks auto actuation only
* Generates Annunciator & red light on cabinet
Auto Unblocks when:
* 2/4 PZR pressure channels are {> 1725} [> 1836] psia (with dead band)
Resetting SIAS
* Unit 1- components may change position (BAM Pumps will stop if on automatically)
* Unit 2- only overridden components will change position, such as CCW N header valves
* Remember, to reset a signal, you must be less than the initiation setpoint or have signal blocked
Discuss Containment Isolation Signal {CIS} [CIAS].
Designed to isolate the Containment from all but essential systems during a LOCA
Auto initiated from:
SIAS Actuated
CNMT Press Hi (2/4) {≥ 5.0} ]≥ 3.5] psig
CNMT Radiation Hi (2/4)
(Modes 1 – 4) 10 R/HR
(Mode 6: When moving recently irradiated fuel) 90Mrem/HR
De-energizes the bistable to actuate
Can be manually actuated from the RTGB
There are NO Blocks of CIS [CIAS]
Resetting Unit 2 CIAS could result in the SBVS fans swapping to the refueling pool from the Annulus if refueling pool high radiation levels (i.e., > 15 mr/hr) are present.
Discuss Main Steam Isolation Signal.
Designed to mitigate the consequences of a main steamline break
Auto initiated from:
S/G Press Low (2/4) ≤ 600 psia
[CNMT Press Hi (2/4) ≥ 3.5 psig]
When 2/4 instruments exceed the actuation setpoint (not auctioneered like RPS)
Can be manually actuated from the RTGB
Interposing Relays: Actuation logic on either S/G will actuate a MSIS on BOTH S/Gs.
Block feature
* Used during controlled cooldown.
* Cannot block Hi CTMT Pressure signal – [ Which is a Unit 2 only signal]
* Block procedurally controlled and similar to blocking SIAS
Unit 2 Only Design
* The Unit 2 MSIV design could allow some backflow of steam from the non-ruptured S/G into containment BEFORE the MSIVs would auto close on low S/G pressure.
* Therefore, by closing the Unit 2 MSIV’s on High CTMT pressure, we would assure that the Unit 2 CTMT pressure rise from the non-faulted S/G is terminated.
This setpoint assumes that the MSIV on the faulted S/G fails to close, which lines up a flowpath from the non-faulted S/G to the faulted S/G through the turbine bldg. steam header.
Discuss Containment Spray Actuation Signal.
Designed to limit containment peak pressure during a LOCA
Auto initiated from:
Unit 1
SIAS Actuated
AND
CNMT Press Hi-Hi (2/4) ≥ 10.0 psig
Unit 2
SIAS Actuated
AND
CNMT Press Hi-Hi (2/4) ≥ 5.4 psig
Energizes to actuate to prevent a failed actuation relay from causing an inadvertent actuation
There is NO Block feature for CSAS
Discuss Recirc Actuation Signal.
Designed to swap injection pump suction to containment sump as RWT empties during LOCA injection phase
Auto initiated from:
RWT Level (2/4) {4 ft} [5.67 ft (6 ft – nominal value)}
Energizes to actuate to prevent a failed actuation relay from causing an inadvertent actuation
There is NO block feature for RAS
Discuss Aux Feedwater Actuation Signal.
Considered part of ESFAS
Auto initiated from:
S/G Level (2/4) ≤ 19 % for {235} [210] seconds without level rising ≥ 29 %
Deenergize to actuate
Discuss ATWS / DSS Actuation Signal.
Protects the RCS pressure boundary from severe over pressure due to a failure of the RPS to trip the reactor when required. DBE for the DSS is total loss of feed with a failure of the RPS to trip the reactor
Auto initiated from:
Hi RCS Pressure (2/4) ≥ 2450 psia
- Setpoint: Fed from PT1103A-D
- Actually set at 2437.5 psia
On 2/4 high pressurizer pressure the DSS actuates to open a line contactor in series with each CEA MG set, de-energizing the CEA bus
Actuation relays are energized to actuate
Alarms when ATWS/DSS channel actuated or bypassed.
No manual actuation – from RTGB
No Block feature– from RTGB
DSS cannot be manually Actuated or Blocked from the RTGB; can be blocked (but not actuated) with a key-switch located on the Actuation Module in the SA & SB Actuation Cabinets
ATI performs continual testing of ATWS circuitry
